package com.ljc.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import javax.annotation.Resource;
import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.ljc.utils.RedisConstants.LOCK_SHOP_KEY;
import static com.ljc.utils.RedisConstants.LOCK_SHOP_TTL;

@Slf4j
@Component
public class CacheClient {
    @Resource
    private StringRedisTemplate stringRedisTemplate;

    public void set(String key, Object value, Long time, TimeUnit unit) {
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, unit);
    }

    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit) {
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    public <R, ID> R queryWithPassThrough(String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit unit) {
        String key = keyPrefix + id;
        //1、从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2、判断是否存在
        if (StrUtil.isNotBlank(json)) {
            //3、存在，直接返回
            return JSONUtil.toBean(json, type);
        }
        //判断命中的是否是空值
        if (json != null) {
            // 返回一个错误信息
            return null;
        }
        //4、不存在，根据id查询数据库
        R r = dbFallback.apply(id);
        //5、数据库中没有该数据，返回错误
        if (r == null) {
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(key, "", time, unit);
            //返回错误信息
            return null;
        }
        //6、存在，写入redis
        this.set(key, r, time, unit);
        //7、返回
        return r;
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    public <R, ID> R queryWithLogicalExpire(String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit unit) {
        String key = keyPrefix + id;
        //1、从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2、判断是否命中
        if (StrUtil.isBlank(json)) {
            //3、未命中，直接返回
            return null;
        }
        //4、命中，需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData(), type);
        //5、判断是否过期
        LocalDateTime expireTime = redisData.getExpireTime();
        if (expireTime.isAfter(LocalDateTime.now())) {
            //5.1、未过期，直接返回店铺信息
            return r;
        }
        //5.2、已过期需要缓存重建
        //6、缓存重建
        //6.1、获取互斥锁
        String LockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(LockKey);
        //6.2、判断是否获取锁成功
        if (isLock) {
            //6.3、获取成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    //重建缓存
                    //查询数据库
                    R r1 = dbFallback.apply(id);
                    //写入redis
                    this.setWithLogicalExpire(key, r1, time, unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unlock(LockKey);
                }
            });
        }
        //6.4、无论失败还是成功，返回商铺信息
        return r;
    }

    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", LOCK_SHOP_TTL, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unlock(String key) {
        stringRedisTemplate.delete(key);
    }
}





